Study On The Technology Of Ni-W-PTFE Alloy Coating Electrodeposition

The alloy coating of Ni—W—PTFE(Polytetrafiuoroethylene) electrodeposition has many specific properties, especially in the term of corrosion-resisting and Self-lubricating, then it is paied attention by more and more researchers.The emphasis of this paper is to survey the alloy of Ni—W—PTFE. There are two indexs considered in total experiments. One is the corrosion rate and another is coefficient of friction.Firstly, the experiments were done by the method of individual factor, through changing the concentrations of every composition in the electroplating solution and electrodeposition parameters, then got a series of coatings and tested, analysed and contrasted the effects on the qualities of coatings here are corrosion-resisting and metallographic structure. According to the results, a certain conclusion about every factor can be made; increasing the concentration of NiSO₄·H₂O can enhance the rate of deposition, but if the concentration is over higher, the growing speed of crystal nuclear is quicker that the forming nuclear, that will not beneficial to form the compacting coating; so effect the corrosion rate and coefficient of friction; W can be induced and slender the crystal grains of the coating; over the higher concentrations will raise the inner stress; The NiCl₂·6H₂O made the fluid electric conductibility enhanced, when the NiCl₂·6H₂O content increased it can cause Cl^- and the Ni²⁺ increases creates corrosion rate reduced; When the PTFE particle content is low, the quantity of Ni²⁺ waited for adsorption still had the earnings, the quantity of composite was increased along with the PTFE particle content increased, when its content surpassed a point, Ni²⁺ in anode could not cover all the surface of PTFE particle, then composite quantity reduces along with its content increased, when the PTFE particle content oversized, the PTFE non-electrical conductivity had the spatial steric effect, was equal to increasing the current density, caused the light-sized pellet particle, was disadvantageous to composite deposits; The H₃BO₃ content has not affected to the coating quality; the C₆H₅ Na₃O₇·3H₂O can help to attain the compacting coating, the higher concentration can lead to the difficult of deposition; the content of lactic acid increases will made corrosion rate became lower, because lactic acid increased, although the complex W increased, deposited the PTFE particle increased, caused the pellet reunion intensify the corrosion rate lower the coefficient of friction higher; the low initial pH is advantageous to separate out H₂, when it became higher, the Ni(0H)2 productions will be create, both of them have disadvantage on coating; the cathode-current density can produce a compactness coating, but the high current density has caused the gap increased; Enhances the temperature, may increased the deposition rate, raise the coating quality, although it can enlarge the liquid loss; the time lengthens can cause coating thick, but a over long time can creates the coating dehiscence.Secondly, on the base of individual factor conclusion, the experiments were made by the means of ortho-design, the object is further to optimize the composition and concentrations of eletrodeposition solution and technology parameters, in the course of electrode-position of Ni—W—PTFE alloy, The results are as follows: NiSO₄·6H₂O 50g·L^-1; Na₂WO₄·2H₂O 50g·L^-1; PTFE 30mL·L^-1; H₃BO₃ 32.5g·L^-1; NiCl₂·6H₂O 35g·L^-1; C₆H₅ Na₃O₇·3H₂O 32.5g·L^-1; lactic acid 12mL·L^-1; Temperature T=45℃; Time t=120min; pH=4.5; Cathode-current density Jc=3.0A·dm^-2; HCHO 5ml·L^-1; Saccharin 0.8 g·L^-1; OP-10 5 mL·L^-1. The coating which was gotten under the better conditions is tested and analysed by the instruments of EDAX, Scanning Electro Microsope(SEM). The results were shown that the coating is made of: Ni 83.01 %, W 11.21%, C 5.19 %, F 0.58%, corrosion rate is 4.9 g·m^-2·h^-1, coefficient of friction is 0.16.